Chemoselective Reductions with Sodium Borohydride and Lithium Borohydride in Mixed Solvents

Abstract

Chemoselective reductions with sodium borohydride and lithium borohydride were examined in mixed solvents containing methanol. Ester, lactone, epoxide, diaryl disulfide, azide, and carboxylic anhydride were reduced chemoselectively in the presence of other reducible groups with sodium borohydride in refluxing t-butyl alcohol or tetrahydrofuran with dropwise addition of methanol. Chemoselectivity of these reductions were better than that of lithium aluminum hydride. On the other hand, ester, lactone, and epoxide were reduced rapidly and chemoselectively with lithium borohydride in mixed solvent containing methanol. Primary amides were reduced chemoselectively in the presence of secondary amide and metal carboxylate with lithium borohydride in MeOH-diglyme. This chemoselectivity is unprecedented. © 1987, The Society of Synthetic Organic Chemistry, Japan. All rights reserved.